2006ApJ...641..357T

We present infrared echelle spectroscopy of three Herbig-Haro (HH) driving sources (SVS 13, B5-IRS 1, and HH 34 IRS) using Subaru IRCS. The large diameter of the telescope and wide spectral coverage of the spectrograph allowed us to detect several H₂and [Fe II] lines in the H and K bands. These include H₂lines arising from v=1-3 and J=1-11, and [Fe II] lines with upper level energies of E/k=(1.1-2.7)x10⁴ K. For all objects the outflow is found to have two velocity components: (1) a high-velocity (-70 to -130 km/s) component (HVC), seen in [Fe II] or H₂emission and associated with a collimated jet; and (2) a low-velocity (-10 to -30 km/s) component (LVC), which is seen in H₂emission only and is spatially more compact. Such a kinematic structure resembles optical forbidden emission line outflows associated with classical T Tauri stars, whereas the presence of H₂emission reflects the low-excitation nature of the outflowing gas close to these protostars. The observed H₂flux ratios indicate a temperature of (2-3)x10³ K and a gas density of 10⁵/cm3 or more, supporting shocks as the heating mechanism. B5-IRS 1 exhibits faint extended emission associated with the H₂-LVC, in which the radial velocity slowly increases with distance from the protostar (by ∼20 km/s at ∼500 AU). This is explained as warm molecular gas entrained by an unseen wide-angled wind. The [Fe II] flux ratios indicate electron densities to be ∼10⁴/cm3 or greater, similar to forbidden-line outflows associated with classical T Tauri stars. Finally, the kinematic structure of the [Fe II] emission associated with the base of the B5-IRS 1 and HH 34 IRS outflows is shown to support disk-wind models.